Approximately 216, and up to 240, healthy males and non-pregnant females, 18 to 49 years old, inclusive, will be enrolled over a 5-month period into this multicenter, randomized, double-blinded, controlled Phase I study. Subjects who meet the entry criteria for the study and provide informed consent will be randomized 2:1 between adjuvanted and unadjuvanted vaccine and placed into one of 6 groups (see table) to receive two doses of an intramuscular subvirion inactivated monovalent influenza A/H5N1 virus vaccine at 3.75, 7.5, or 15 mcg given with the adjuvant AS03 or diluent (N=216, up to 240). All eligible subjects will receive 2 doses separated by approximately 21 days.